1. Technical Field
The present disclosure relates generally to a micro inverter of a solar power system and a method of operating the same, and more particularly to a micro inverter with a power boosting function of a solar power system.
2. Description of Related Art
The research and development of alternative energy resources have become the major issue and key polity in many developed countries over the world since the two oil crises of the 1970s. In addition, the oil prices rise because the industrial development promotes the global economic growth and results in the rapid growth of the oil demand. Hence, environmental issues have received more attention recently, and more particularly to the effects of carbon dioxide on air pollution. In order to effectively reduce our dependence on oil as a source of energy, a variety of renewable resources, such as solar energy, wind energy, and so on, are researched and developed.
Because the solar energy has the pollution-free and public harm-free characteristics and is further inexhaustible in supply and always available for use, the solar energy has high potential applications and developments. Recently with the rapidly development of the high-efficiency solar cells, this topic has been gradually promoted by making policies in many developed countries, such as Europe countries, the United States, Japan, and so on.
The conventional common structure of the solar photovoltaic generation system is mainly that the solar photovoltaic module array is in series and/or in parallel. However, the structure of the solar photovoltaic module array has following disadvantages:
It is difficult to consider MPPT function for all in-series or in-parallel solar photovoltaic modules so that the utilization ratio of the solar photovoltaic modules is lower, the influence of the partial shading is serious, and the system expansion is inelastic. In order to overcome the above-mentioned problems, the technology of micro inverters is developed.
Reference is made to FIG. 1 which is a schematic circuit block diagram of a related art solar photovoltaic module and a related art micro inverter. The solar photovoltaic module 10A generates a solar photovoltaic module output power Pv, and the micro inverter 20A generates a micro inverter output power Pm. For convenience, the detailed operation of the relationship between the solar photovoltaic module output power Pv and the micro inverter output power Pm is described hereinafter as follows, and reasonable assumed data are exemplified. It is assumed that the rated output power value of the solar photovoltaic module is 250 watts when the ambient temperature around the solar photovoltaic module is 25° C. If the micro inverter 20A with the 215-watt rated output power value is selected to coordinate with the solar photovoltaic module 10A, the maximum output power of the micro inverter is merely 215 watts even though the solar photovoltaic module output power Pv is 250 watts. In other words, the redundant output power between the output power value of the solar photovoltaic module 10A and the rated output power value of the micro inverter 20A is unavailable so that the utilization ratio of the solar photovoltaic module output power Pv is low. Hence, the better solution to overcome the problem is that the micro inverter 20A with greater rated output power value is selected to coordinate with the solar photovoltaic module 10A so that the micro inverter 20A can completely and fully output the solar photovoltaic module output power Pv, thus increasing the utilization ratio of the solar photovoltaic module output power Pv.
The relationship between the output power value of the solar photovoltaic module 10A and the ambient temperature is negative temperature coefficient. That is, the output power value of the solar photovoltaic module 10A is lower when higher ambient temperature around the solar photovoltaic module 10A. Reference is made to FIG. 2 which is a schematic view of a relationship between the output power value of the solar photovoltaic module and the ambient temperature. Comparing to the above-mentioned example, the solar photovoltaic module output power Pv is 230 watts when the ambient temperature is increased to 40° C.; and also, the solar photovoltaic module output power Pv is 210 watts when the ambient temperature is further increased to 60° C. Therefore, the micro inverter 20A with the 250-watt rated output power value can completely and fully output the solar photovoltaic module output power Pv whether the ambient temperature is 40° C. or 60° C. so that the utilization ratio of the solar photovoltaic module output power Pv is increased.
On the contrary, the solar photovoltaic module output power Pv is 280 watts when the ambient temperature is reduced to 0° C. Because the micro inverter 20A with the 250-watt rated output power value is selected to coordinate with the solar photovoltaic module 10A, the maximum output power of the micro inverter is merely 250 watts even though the solar photovoltaic module output power Pv is 280 watts. In other words, the redundant output power between the output power value of the solar photovoltaic module 10A and the rated output power value of the micro inverter 20A is unavailable so that the utilization ratio of the solar photovoltaic module output power Pv is low.
Accordingly, it is desirable to provide a micro inverter of a solar power system and a method of operating the same to increase output power of the micro inverter without increasing additional solar photovoltaic module devices and merely executing a power boosting function according to the feature of the negative temperature coefficient so as to increase power generation efficiency, reduce power generation costs, increase operation adaptation, and widely apply to different regions and countries.